Compartment Syndrome, which may cause Volkmann's Ischemic Contracture, occurs when bleeding and/or swelling interfere with proper blood circulation in enclosed groups of muscles and nerves. In the body, certain muscle groups, along with their indwelling blood vessels and nerve tissue, are covered by fascia, a noncompliant collagenous membrane, forming what is termed a “compartment.” With bleeding and/or swelling, compartment pressure (CP) within the compartment increases, causing a decrease in venous, capillary, and ultimately, arterial blood flows. The network of blood vessels in the compartment becomes compressed by the pressure differential between the CP (exterior to the blood vessel) and the blood vessel interior; this impedes the rate of blood flow volume (RBFV) through the blood vessel network. Swelling occurs within the tissue, further restricting the blood flow. Although, according to the well-known Windkessel Theory, an occasional fluctuation in blood pressure pushes a bolus of blood through the blood vessel network, this normally is insufficient to reverse the continual deterioration of the muscle mass or maintain tissue viability. As the RBFV decreases over sufficient time and as CP rises, muscle viability deteriorates, with both nerve and muscle cells eventually dying from the lack of nutrients. Compartment Syndrome creates clinical signs such as acute pain and a progressive loss of muscle and nerve functions, usually in lower leg and forearm compartments, or possibly other body areas such as the wrist, buttocks, thigh, and upper arm. Potentially, any muscle of the body can experience a compartment syndrome. As pressures build over time and blood flow remains at abnormally low levels, myoneural necrosis occurs, leading to permanent injury (Volkmann's Contracture) and possible amputation of the limb.
Compartment Syndrome most commonly occurs with trauma or substantial injury to the body, such as a broken or crushed arm or leg (frequently resulting in Acute Compartment Syndrome), with some occurrences of Compartment Syndrome coming from tight bandages or surgery (which can result in Acute Compartment Syndrome) or extended exercise (Chronic [exertional] Compartment Syndrome). After trauma to a given area, a person may experience pain or an inability to use the muscles in the injured area. Surgery, such as cutting the fascia, can be performed to decrease the compartment pressure and increase blood flow to the muscle. As the fascia is substantially inelastic, swelling increases pressure within the body compartment, and muscles, blood vessels, and nerves within the compartment are compressed.
Even experienced physicians can have trouble making a reliable diagnosis of Compartment Syndrome. Known testing for Compartment Syndrome may include pressure measurement in the compartment by inserting a needle attached to a pressure meter. Compartment pressure of greater than 30-45 mmHg or pressures within 30 mmHg of the diastolic blood pressure indicate the presence of Compartment Syndrome if sufficient time has taken place.
U.S. Pat. No. 5,746,209 to Yost et al., entitled “Method of and Apparatus for Histological Human Tissue Characterization Using Ultrasound” discloses the use of ultrasound for determining histological characteristics of tissue by converting the return of energy pulses into numerical terms, useful in a diagnosis for the development of pressure ulcers. However, Yost et al. '209 does not address the diagnosis of Compartment Syndrome.
There is a need in the art to provide non-invasive determinations of CP associated with Compartment Syndrome. The present invention addresses this and other needs.